It seems that the "proof" still really isn't, from the article: "only the most senior U.K. officials are believed to have seen the intelligence, which the CIA

It seems that the "proof" still really isn't, from the article: "only the most senior U.K. officials are believed to have seen the intelligence, which the CIA awarded a strong but not cast-iron classification of certainty." Note the weasel words. https://en.wikipedia.org/wiki/Weasel_word https://en.wikipedia.org/wiki/Weasel_word